A commonly employed method to interlock with a manual control plug is by using a magnetic solenoid which blocks the racking of the circuit breaker when the manual control plug is disconnected. With this method, auxiliary control voltage, which is used to power the auxiliary features of the circuit breaker, energizes the magnetic solenoid and releases the interlock and allows the circuit breaker to be racked into the connect position. With the magnetic solenoid method of interlocking, the presence of auxiliary control voltage is required in order to rack the circuit breaker into or out of connected position. In situations where the auxiliary power is not available, the circuit breaker is not able to be installed or removed from the connected position. The requirement to install the manual control plug and the use of a magnetic solenoid adds an additional requirement of the presence of auxiliary voltage in order to install or remove the circuit breaker and is not acceptable by many customers due to the rare cases where installation or removal needs to be done without auxiliary voltage.
Another conventional solution for this problem involves using an automatic connecting auxiliary control connector where the connection for the auxiliary control voltage is made as part of the racking operation. This method requires the use of a specially designed plug and socket which is prone to misalignment. There also exists a configuration to install the manual control plug at the base of the racking truck in order to allow racking, but the configuration requires an alignment of the plug and socket and is prone to misalignment.
Thus, there is a need to provide a racking interlock structure that prevents racking of a circuit breaker into or out of the connect position without the control plug connected and without requiring auxiliary voltage or special alignment features of a plug and socket.